This article (better sourced) says the opposite:
http://nymag.com/daily/intelligencer/2015/08/fox-news-picked-trump-over-megyn-kelly.html
The article you linked to simply says that after the debate debacle they scrambled to get Trump back on THEIR airwaves because he draws an audience and big ratings which Ailes knows they cannot afford to lose.
This from your linked article speaks volumes:
after Trump told Sean Hannity in a weekend phone call
that he was “never doing Fox again,” appeared on four non-Fox public-affairs shows on Sunday,
and did interviews with Today and Morning Joe on Monday,
Ailes raised the white flag and picked up the phone on Monday morning.